In general, an imaging apparatus includes photoelectric conversion elements (light-receiving elements, photodiodes, or imaging elements) formed on a silicon semiconductor substrate. Meanwhile, the light absorption coefficient of silicon (Si) is uniquely determined when the wavelength of incident light is determined. Accordingly, in order to cause light, particularly light of red to a near-infrared wavelength region to be efficiently absorbed in the silicon semiconductor substrate, the photoelectric conversion elements are required to be formed in a region of the silicon semiconductor substrate in a place deep (specifically, for example, about 10 μm) from a light incident surface. This represents that the aspect ratio of the photoelectric conversion elements increases as pixels in the imaging apparatus are miniaturized.
However, the increase in the aspect ratio of the photoelectric conversion elements causes a problem such as inter-pixel color mixture in which light incident on another photoelectric conversion element adjacent to one photoelectric conversion element is also incident on the one photoelectric conversion element. When the aspect ratio of the photoelectric conversion elements is decreased to reduce the inter-pixel color mixture, a problem such as reduction in the sensitivity of the photoelectric conversion elements from red to the near-infrared wavelength region is caused. In addition, Si cannot detect infrared light having a wavelength of 1.1 μm or greater in principle since its band gap energy is 1.1 eV. It is possible to detect infrared light with, for example, a photoelectric conversion layer having the laminated structure of an InP layer and an InGaAs layer instead of Si (see, for example, Japanese Patent Application Laid-open No. 2012-244124). That is, a light-receiving element array disclosed in the publication of the patent application is a light-receiving element array having light-receiving sensitivity in a near-infrared wavelength region and formed in the laminated body of a group III-V compound semiconductor, the light-receiving element array having arranged therein a plurality of light-receiving parts having band gap energy corresponding to the near-infrared wavelength region. Further, the light-receiving parts have a pn-junction at the tip end of a first conductivity type region formed by selective diffusion. In addition, a second conductivity type region is positioned between the light-receiving parts so as to divide the light-receiving parts. Here, the second conductivity type region is formed on the basis of an ion injection method or a selective diffusion method.